System and method for an improved interconnect structure

ABSTRACT

Presented herein are an interconnect structure and method for forming the same. The interconnect structure includes a contact pad disposed over a substrate and a connector disposed over the substrate and spaced apart from the contact pad. A passivation layer is disposed over the contact pad and over connector, the passivation layer having a contact pad opening, a connector opening, and a mounting pad opening. A post passivation layer including a trace and a mounting pad is disposed over the passivation layer. The trace may be disposed in the contact pad opening and contacting the mounting pad, and further disposed in the connector opening and contacting the connector. The mounting pad may be disposed in the mounting pad opening and contacting the opening. The mounting pad may be separated from the trace by a trace gap, which may optionally be at least 10 μm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 14/996,016, filed on 14 Jan. 2016 and entitled “System and Method for an Improved Interconnect Structure,” which application is a divisional of U.S. patent application Ser. No. 13/799,157, filed on 13 Mar. 2013 and entitled “System and Method for an Improved Interconnect Structure,” now U.S. Pat. No. 9,275,925, issued on 1 Mar. 2016, which claims the benefit of U.S. Provisional Application No. 61/778,228, filed on 12 Mar. 2013 and entitled “System and Method for Improved Interconnect Structure,” which applications are hereby incorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductor layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.

Solder ball grid arrays are also a technique sometimes used to join substrate, dies or packages, with an array of solder balls deposited on the bonding pads of a first substrate, and with a second substrate, die or package joined at its own bonding pad sites to the first pad via the solder balls. Solder balls may be formed on a pad as liquid solder, and then solidified for additional processing. The environment with the solder balls is subsequently heated to melt the solder balls and the packages compressed to cause the solder balls to contact the upper and lower pads.

In some systems, a trace may be disposed over an upper protective layer, above the passivation layer. Such traces may be referred to as post-passivation interconnects (PPIs). Such PPIs may be used to connect a trace on, for example, a substrate or in a redistribution layer (RDL), to a pad or land below the passivation layer. The mounting pads may have a solder ball as part of a ball grid array, or may have another package connector, permitting a second package to be mounted and still be in electrical communication with the lands below the passivation layer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIGS. 1 through 9 illustrate cross-sectional views of intermediate steps in forming an interconnect according to an embodiment;

FIG. 10 illustrates a perspective view of an interconnect structure according to an embodiment;

FIG. 11 illustrates a top view of an interconnect structure according to an embodiment; and

FIG. 12 is a flow diagram illustrating a method for forming an interconnect structure according to an embodiment.

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION

The making and using of the presented embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the described conductive interconnect or joint (an “interconnect”), and do not limit the scope of the disclosure.

Embodiments will be described with respect to a specific context, namely making and using interconnects useful in, for example, fan-in or fan-out wafer level packaging or Wafer Level Chip Scale Package (WLCSP) assemblies. Other embodiments may also be applied, however, to other electrically connected components, including, but not limited to, package-on-package assemblies, die-to-die assemblies, wafer-to-wafer assemblies, die-to-substrate assemblies, in assembling packaging, in processing substrates, interposers, substrates, or the like, or mounting input components, boards, dies or other components, or for connection packaging or mounting combinations of any type of integrated circuit or electrical component.

The embodiments of the present disclosure are described with reference to FIGS. 1 through 12, and variations of the embodiments are also discussed. Throughout the various views and illustrative embodiments of the present disclosure, like reference numbers are used to designate like elements. Additionally, the drawings are intended to be illustrative, are not to scale and not intended to be limiting. Note that, for simplification, not all element numbers are included in each subsequent drawing. Rather, the element numbers most pertinent to the description of each drawing are included in each of the drawings.

FIG. 1 is a cross-sectional view representatively illustrating formation of a contact pad 102 and connector 104 of an interconnect according to an embodiment. A contact pad 102 and a connector 104 may be formed on a die substrate 106. The contact pad 102 and connector 104 may be spaced apart. In an embodiment, the contact pad 102 and connector 104 may be formed in a single process step, for example, through a masking and deposition process, through a damascene process, or another suitable process. The contact pad 102 and connector 104 may be disposed in the same level, such as on the die substrate 106, in a same metallization layer, or the like. In an embodiment, the connector 104 may be disposed in a level different from the contact pad 102, for example in a higher metallization layer, over a passivation layer above the contact pad 102, or the like.

Additionally, the contact pad 102 and connector 104 may be a conductive material, such as copper (Cu), tungsten (W), gold (Au), silver (Ag), aluminum, (Al), lead (Pb), tin (Sn), alloys of the same, and/or the like. The die substrate 106 may be a semiconductor, such as silicon (Si), gallium arsenide (GaAs), silicon-on-insulator (SoI) and/or the like. In an embodiment, the die substrate 106 may be a redistribution layer (RDL), intermetal dielectric (IMD), interlayer dielectric (ILD) and/or the like.

The contact pad 102 and connector 104 may be formed using photolithography and deposition processes such as plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), sputtering, or another deposition process. For example, the contact pad 102 and connector 104 regions may be defined by a mask, and a conductive material deposited in openings in the mask then planarized to form the contact pad 102 and connector 104. A chemical mechanical polish, for example, may be used to planarize the contact pad 102 and connector 104. While the contact pad 102 and connector 104 are illustrated as being disposed over the die substrate 106, the contact pad 102 and connector 104 may be disposed in the die substrate 106, with the upper surface of each exposed. For example, in one embodiment, the contact pad 102 and connector 104 may be formed using a damascene process. In such an embodiment, the die substrate 106 may be etched other otherwise processed to form recesses, and a conductive material may be deposited in the recesses, with excess material removed via planarization, leaving the contact pad 102 and the connector 104 in the die substrate 106 recesses.

FIG. 2 is a cross-sectional view representatively illustrating formation of a passivation layer 202 according to an embodiment. An insulating layer may comprise a passivation layer 202 which may be deposited over the die substrate 106 and over a portion of the contact pad 102 and connector 104. In an embodiment, the passivation layer 202 may be masked or otherwise formed to have a contact pad opening 204 exposing a portion of the contact pad 102. A connector opening 206 and a mounting pad opening 208 may be formed in the passivation layer 202 to each expose a portion of the connector 104.

FIG. 3 is a cross-sectional view representatively illustrating formation of a protective layer 302 according to an embodiment. The insulating layer may further comprise a protective layer 302 which may be formed over the passivation layer 202, and which may be a polymer, polyimide, nitride, oxide, or other non-conductive layer. The protective layer 302 may be formed via a masking and deposition process, via a deposition and etching process, or the like. In an embodiment, the protective layer 302 may be formed to cover the passivation layer, and contacting the contact pad 102 through the contact pad opening 204 and also contacting the connector 104 through the connector opening 206 and mounting pad opening 208.

FIG. 4 is a cross-sectional view representatively illustrating formation of a post-passivation layer according to an embodiment. A post passivation layer may comprise a trace 402 and a mounting pad 404. The trace 402 and mounting pad 404 may be disposed in a layer or level higher than the contact pad 102 and connector 104, for example, over the protective layer 302, in a higher metallization layer, or the like. The trace 402 may be formed in the contact pad opening 204 with a trace contact pad portion 412 in contact with the contact pad 102. The trace 402 and mounting pad 404 may be conductive material such as a metal such as copper (Cu), tungsten (W), gold (Au), silver (Ag), aluminum, (Al), lead (Pb), tin (Sn), alloys of the same, or the like. The trace 402 may also have a trace connector via 406 disposed in the connector opening 206 and contacting the connector 104. Thus, in an embodiment, the trace 402 may electrically connect the contact pad to the connector 104. The mounting pad 404 may be formed with a mounting pad via 408 disposed in the mounting pad opening 208 and in contact with the connector 104. In an embodiment, the mounting pad 404 may have an upper mounting pad portion 416 disposed over, or above, the upper surface of the protective layer 302.

The trace 402 and mounting pad 404 are illustrated as being in direct contact with the contact pad 102 and connector 104, however, the contact pad 102 and connector 104 may have one or more outer layers, such as seed layers, barrier layers, anticorrosion layers and/or the like, and the trace 402 or mounting pad 404 may contact the contact pad 102 or connector 104 by way of these outer layers. The trace 402 and mounting pad 404 may also comprise one or more outer layers, and may contact the contact pad 102 or connector through these outer layers.

The upper mounting pad portion 416 may be separated from, or spaced apart from, the trace 402 by a trace gap 414. The trace 402 may be electrically connected to the mounting pad 404 by way of the connector 104, but may avoid direct contact with the mounting pad 404 by a separation due to the trace gap 414.

In an embodiment, the trace 402 and the mounting pad 404 may be PPI structures. The trace 402 and mounting pad 404 may be formed through deposition, plating or another technique. In an embodiment, the trace 402 and mounting pad may be formed by masking and metal deposition, or may be masked and etched after deposition.

FIG. 5 is a cross-sectional view of the application of a mounting structure 502 to the mounting pad 404 according to a representative embodiment. The mounting structure 502 may be formed on a mounting pad upper surface 410. In an embodiment, the mounting structure 502 may be solder, a metal such as copper (Cu), gold (Au), aluminum, (Al), lead (Pb), tin (Sn), nickel (Ni), palladium (Pd) and/or the like. The mounting structure may also be a combination of materials such as nickel and palladium or nickel, palladium and gold that are formed for example, through a process such as electroless nickel electroless palladium (ENEP) or electroless nickel electroless palladium immersion gold (ENEPIG). In an embodiment, the trace gap 414 may be sized to avoid permitting or otherwise reduce the opportunity for material on the mounting pad 404 wetting the trace 402 and forming a weak joint. Separation of the mounting pad 404 from the trace 402 by a trace gap 414 prevents or otherwise reduces the opportunity of mounting structure 502 wetting the trace 402 and forming a “bird beak” at the trace-to-mounting pad connection point. Such irregular “bird beak” structure tends to create stress points where the mounting structure 502 contacts the trace 402, leading to stress cracking of the mounting structure 502 or separation of the mounting structure from the mounting pad 404. Eliminating or otherwise reducing irregularities in mounting structure 502 leads to a more robust joint.

In one embodiment, the mounting structure 502 may be applied to the mounting pad 404 so that the mounting structure contacts the mounting pad upper surface 410, and avoids the sides of the upper mounting pad portion 416. In such an embodiment, the mounting structure 502 may contact and cover all of, or a portion of, the mounting pad upper surface 410. In another embodiment, the mounting structure 502 may contact, or wet, at least a portion of the sides of the upper mounting pad portion 416 and at least a portion of the mounting pad upper surface 410. In yet another embodiment, the mounting structure 502 may contact the entire mounting pad upper surface 410 and contact a portion of the upper mounting pad portion 416 around the entire perimeter of the upper mounting pad portion 416, extending over the edge of the upper mounting pad portion 416 partially down the sidewall.

FIG. 6 is a cross-sectional view of the application of molding compound 602 according to a representative embodiment. In one embodiment, the molding compound 602 may be a nonconductive material, such as an epoxy, a resin, a moldable polymer, and/or the like. The molding compound 602 may be formed to provide lateral support to the mounting structure 502 during subsequent processing such as reflow.

FIG. 7 is a cross-sectional view illustrating molding of the molding compound 602 according to an embodiment. The molding compound 602 may be shaped or molded using for example, a mold 704. A release compound 702 may be optionally applied to the mold 704 to prevent or otherwise reduce adhesion of the molding compound 602 to the mold 704. The mold 704 may have a border or other feature for retaining molding compound 602 when the mold 704 is applied to the molding compound 602.

The molding compound 602 may be formed by the mold 704 using a layer of release compound 702 thick enough to compress the molding compound 602 while still separating the mold 704 from the mounting structure 502. The mold 704 may also be configured to accept one or more mounting structure 502 by way of recesses (not shown) formed in the mold 704. In an embodiment, the mold 704 may be used to pressure mold the molding compound 602 to force the molding compound 602 into openings and recesses, and may avoid air pockets or the like in the molding compound 602. In an embodiment, the molding compound 602 may be injection molded, with the mold 704 placed over the mounting structure 502 and a molding compound introduced after the mold 704 is placed.

FIG. 8 is a cross-sectional view representatively illustrating a mounting structure 502 with cured molding compound 602. The molding compound 602 may be cured, and the mold 704 (FIG. 7) and release compound 702 (FIG. 7) removed. The molding compound 602 may be applied while substantially liquid, and then may be cured through a chemical reaction, such as in an epoxy or resin. In another embodiment, the molding compound 602 may be an ultraviolet (UV) cured polymer applied as a gel or malleable solid capable of being disposed on the trace 402, on the protective layer 302 and around or conforming to the mounting structure 502 surface. The optional application of the release compound 702 may permit parting of the mold 704 from the molding compound 602, and may be used in an embodiment where the molding compound 602 is an epoxy or resin to prevent or otherwise minimize adhesion of the molding compound 602 to the mold 704 surface.

In an embodiment, the molding compound 602 may be molded over a lower portion of the mounting structure 502. An upper portion of the mounting structure 502 may extend above an uppermost surface of the molding compound 602 and be exposed through the molding compound 602. The molding compound 602 retains this shape during activation or reflow. For example, where the mounting structure 502 is solder or another metal, the mounting structure 502 may be reflowed for attaching a second substrate. In such an example, the molding compound 602 may confine solder mounting structures 502 and prevent or otherwise reduce bridging between adjacent mounting structures during the reflow process.

A plasma cleaning process may optionally be performed. In an embodiment, the plasma clean process may clean the mounting structure 502 and remove any residual release compound 702 or molding compound 602.

FIG. 9 is a cross-sectional view illustrating a mounting a second substrate 902 on the mounting structure 502. The mounting structure 502 material may be activated to attach the second substrate 902, thereby forming an electrical connection between the contact pad 102 on the first substrate 802 and the second substrate 902. For example, in an embodiment, the mounting structure 502 may be solder or another metal. The mounting structure 502 may be reflowed, or heated to a melting point, and the second substrate 902 may be mounted on the mounting structure 502, and the mounting structure 502 subsequently solidified.

In an embodiment, the second substrate 902 may have lands 904, which may be joined to the mounting structure 502. The second substrate 902 may be a die, wafer, interposer, or another electrical component. Thus, the second substrate 902 or devices disposed thereon may be electrically connected to the contact pad 102.

FIGS. 10 and 11 illustrate a perspective view and a top view, respectively, of an interconnect structure moo according to a representative embodiment. The interconnect structure moo illustrated in FIGS. 10 and 11 is shown, for clarity, without the substrate 106, passivation layer 202, protective layer 302 or mounting structure 502 shown in FIGS. 1-9.

The mounting pad 404 has an upper mounting pad portion 416 that is disconnected or spaced apart from the trace 402 by a trace gap 414 in the region where a mounting structure 502 (FIGS. 5-9) is applied to the upper mounting pad portion 416. The upper mounting pad portion 416 is connected to the trace 402 by way of the connector 104 disposed in a different level than the upper mounting pad portion 416. The trace connector via 406 and mounting pad via 408 connect the trace 402 and upper mounting pad portion 416 to the connector 104, respectively. The connector 104 may comprise connector contact pad portions 1102 that accept the trace connector via 406 and mounting pad via 408. The connector contact pad portions 1102 may be formed having a size greater than the trace connector via diameter 1110 and mounting pad via diameter 1108. Additionally, the trace 402 may comprise a trace contact portion 1104, which may be formed having a size greater than the trace connector via diameter 1110.

The upper mounting pad portion 416 may be sized, for example, according to the material characteristics or a predetermined size of the mounting structure 502. In an embodiment, the upper mounting pad portion 416 may have a size or diameter greater than the mounting pad via 408. In an embodiment, the trace gap spacing 1106 may be about 10 μm or greater, which may be sufficient to prevent or otherwise minimize bridging of a mounting structure 502 (FIGS. 5-9) to the trace. The trace gap spacing 1106 may be adjusted to account for different geometries or disposition of the trace 102 in relation to the upper mounting pad region 416, to account for varying mounting structure 502 (FIGS. 5-9) shape and materials, to account for varying processing methods, or to account for another factor. Additionally, the trace connector via diameter 1110 and mounting pad via diameter 1108 may each be about 20 μm or greater. The via diameters 1110 and 1108 may each be independently varied to accommodate varying lengths or materials of the vias 406 and 408.

FIG. 12 is a flow diagram representatively illustrating a method 1200 for forming an interconnect structure according to an embodiment. In block 1202, a contact pad and connector may be provided by forming the contact pad and connector on a die substrate, for example, or in a metallization layer. In block 1204, a passivation layer may optionally be formed over at least a portion of the contact pad and a portion of the connector. Openings exposing the contact pad and connector may be formed during passivation layer formation, or may be created after the passivation layer is formed. In block 1206, a protective layer may be formed over the contact pad and connector, with openings exposing the contact pad and connector. In block 1208, a post passivation interconnect layer may be formed over the protective layer. A trace and a mounting pad may be formed as part of the post-passivation interconnect layer, with the trace connecting the mounting pad to the connector and the mounting pad connected to the connector but spaced apart from the trace.

In block 1210, a mounting structure may be formed. In block 1212, a molding compound may be applied and in block 1214, the molding compound may optionally be pressure molded. The molding compound may be applied in block 1212 as a liquid, and a mold with an optional release compound may be used to form or pressure mold the molding compound around the mounting structure. The molding compound may also be formed over and covering the post-passivation layer, including the trace. In block 1216, a second substrate may be mounted to the mounting structure and affixed.

An interconnect structure according to a representative embodiment may comprise a mounting pad disposed over a substrate and at a first level, a connector disposed at a second level over the substrate and electrically connected to the mounting pad, and a trace disposed over the substrate and at a level above the second level. The trace may be electrically connected to the connector and electrically connected to the mounting pad by way of the connector. The trace may be spaced apart from the mounting pad.

A representative embodiment of a structure may comprise a contact pad disposed over a substrate, a connector disposed over the substrate and spaced apart from the contact pad, and an insulating layer comprising a passivation layer disposed over the contact pad and over connector. The passivation layer may have a contact pad opening, a connector opening and a mounting pad opening. A post-passivation layer may be disposed over the passivation layer, and may comprise a trace and a mounting pad. The trace may be disposed in the contact pad opening and may contact the mounting pad. The trace may be further disposed in the connector opening and may contact the connector. The mounting pad may be disposed in the mounting pad opening and may contact the connector, and the mounting pad may be separated from the trace by a trace gap.

A method of forming an interconnect structure according to a representative embodiment may comprise providing a contact pad and a connector over a substrate, forming a passivation layer over at least a portion of the contact pad and over at least a portion of the connector and forming a post-passivation layer over the passivation layer. Forming the post passivation layer may comprise forming a trace on the contact pad and on the connector and forming a mounting pad on the connector and spaced apart from the trace.

A method of forming an interconnect structure according to a representative embodiment may comprise providing a contact pad and a connector over a substrate, forming a passivation layer over at least a portion of the contact pad and over at least a portion of the connector, and forming a post-passivation layer over the passivation layer, where forming the post-passivation layer comprises forming a trace on the contact pad and on the connector, where the trace has a major axis extending in a direction substantially parallel to the major surface of the substrate, and forming a mounting pad on the connector and spaced apart from the trace in a direction substantially parallel to the major surface of the substrate. The method may further comprise forming a protective layer over the passivation layer, and forming the post-passivation layer over the protective layer. The method may further comprise forming a contact pad opening, a connector via opening and a mounting pad opening in the passivation layer and in the protective layer. The step of forming the mounting pad may comprise forming an upper mounting pad portion above the protective layer, and forming a mounting pad via disposed in the mounting pad opening and extending from the upper mounting pad portion to the connector. The step of forming the trace may comprise forming a trace contact pad portion disposed in the contact pad opening, and forming a trace connector via disposed in the connector opening. The mounting pad may be spaced apart from the trace by a distance of 10 μm or greater, and/or the mounting pad and connector may be formed in a same level. The method may further comprise forming a mounting structure disposed on the mounting pad. The mounting structure may comprise at least one of solder, a metal, copper (Cu), gold (Au), aluminum (Al), lead (Pb), tin (Sn), nickel (Ni), and/or palladium (Pd).

A method of forming an interconnect structure according to a representative embodiment may comprise providing a connector over a substrate, where the connector is disposed at a second level below a first level, providing an insulating layer disposed over the substrate and over the connector, forming a mounting pad disposed over the insulating layer at the first level (where the mounting pad may be electrically connected to the connector), and forming a trace disposed over the insulating layer and at the first level, where the trace has a major axis extending in a direction substantially parallel to the major surface of the substrate, the trace spaced apart from the mounting pad in a direction substantially parallel to the major surface of the substrate. The trace may be electrically connected to the connector and the mounting pad by way of the connector. The method may further comprise a step of forming a contact pad disposed over the substrate at the second level, where the contact pad may be electrically connected to and in physical contact with the trace, and forming a mounting structure disposed on the mounting pad. The step of forming the mounting pad may comprise forming a mounting pad via and an upper mounting pad portion, where the mounting pad via extends from the upper mounting pad portion to the connector. The step of forming the insulating layer may comprise a step of forming a passivation layer disposed over a portion of the contact pad and/or a portion of the connector. Forming the insulating layer may further comprise forming a protective layer disposed over the passivation layer, where the trace and/or the mounting pad are disposed over at least a portion of the protective layer. The method may further comprise a step of disposing a molding compound over the trace and around the mounting structure. The trace and/or the mounting pad may be in physical contact with the connector.

In an embodiment, a method of forming an interconnect structure comprises steps of: forming a connector over a substrate; forming a contact pad over the substrate; forming a mounting pad over the connector, the mounting pad electrically coupled to the connector; forming a trace over the connector and the contact pad, the trace having a major axis extending in a direction substantially parallel to a major surface of the substrate, the trace spaced apart from the mounting pad in a direction substantially parallel to the major surface of the substrate, the connector electrically interposed between the trace and the mounting pad; and forming a mounting structure on the mounting pad. Forming the trace may comprise forming an insulating layer over the contact pad and the connector, and patterning a contact pad opening and a connector opening in the insulating layer, the contact pad being exposed in the contact pad opening, the connector being exposed in the connector opening. Forming the trace may also comprise forming a metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the contact pad and the connector. The connector and the contact pad may be formed at a same level. Forming the mounting pad may comprise depositing a metal layer, the metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the connector. The method may further comprise a step of disposing a molding compound over the trace and around the mounting structure.

In another embodiment, a method of forming an interconnect structure comprises a step of forming a trace at a first level over a substrate, the trace having a major axis extending in a direction substantially parallel to a major surface of the substrate, the trace spaced apart from a mounting pad in a direction substantially parallel to the major surface of the substrate, the trace electrically connected to a connector and electrically connected to the mounting pad by way of the connector, wherein the connector is disposed at a second level below the first level. The method may further comprise a step of forming a contact pad at the second level. Forming the trace may comprise steps of forming an insulating layer over the contact pad and the connector, and patterning the insulating layer to expose the connector. Forming the trace may also comprise patterning the insulating layer to expose the contact pad. Forming the trace may also comprise depositing a metal line, the metal line extending continuously from the contact pad to the connector, the metal line extending over an upper surface of the insulating layer. The trace and the mounting pad may be formed substantially simultaneously. The method may further comprise a step of disposing a molding compound over the trace.

In yet another embodiment, a method of forming an interconnect structure comprises steps of: providing a contact pad and a connector over a substrate, the substrate having a major surface; forming an insulating layer over the contact pad and the connector, the insulating layer having a first opening over the contact pad, a second opening over the connector, and a third opening over the connector; forming a trace over the insulating layer, the trace extending through the first opening to the contact pad and through the second opening to the connector; forming a mounting pad on the connector, the mounting pad extending through the third opening, the connector being electrically interposed between the trace and the mounting pad; and forming a mounting structure on the connector. The mounting pad may extend over an upper surface of the insulating layer. The mounting structure may comprise a solder material. Forming the trace and forming the mounting pad may be performed substantially simultaneously. The mounting structure may extend along a sidewall of the mounting pad. The method may further comprise a step of disposing another insulating material over the trace and around the mounting structure. The another insulating material may be interposed between the mounting pad and the trace.

Although embodiments of the present disclosure and certain advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, it will be readily understood by those skilled in the art that many of the features, functions, processes, and materials described herein may be varied while remaining within the scope of the present disclosure. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, articles of manufacture, composition of matter, means, methods, or steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, articles of manufacture, compositions of matter, means, methods, or steps, presently existing or later developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, articles of manufacture, compositions of matter, means, methods, or steps. 

What is claimed is:
 1. A method of forming an interconnect structure, the method comprising: forming a connector over a substrate; forming a contact pad over the substrate; forming a mounting pad over the connector, the mounting pad electrically coupled to the connector; forming a trace over the connector and the contact pad, the trace having a major axis extending in a direction substantially parallel to a major surface of the substrate, the trace spaced apart from the mounting pad in a direction substantially parallel to the major surface of the substrate, the connector electrically interposed between the trace and the mounting pad; forming a mounting structure on the mounting pad; and disposing a molding compound over the trace and around the mounting structure.
 2. The method of claim 1, wherein the forming of the trace comprises: forming an insulating layer over the contact pad and the connector; and patterning a contact pad opening and a connector opening in the insulating layer, the contact pad being exposed in the contact pad opening, the connector being exposed in the connector opening.
 3. The method of claim 2, wherein the forming of the trace comprises forming a metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the contact pad and the connector.
 4. The method of claim 2, wherein the connector and the contact pad are formed at a same level.
 5. The method of claim 2, wherein the forming of the mounting pad comprises depositing a metal layer, the metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the connector.
 6. The method of claim 1, further comprising: reshaping the molding compound such that a topmost surface of the molding compound is below a topmost surface of the mounting structure.
 7. A method of forming an interconnect structure, the method comprising: forming a connector over a substrate; forming a contact pad over the substrate; forming a mounting pad over the connector, the mounting pad electrically coupled to the connector; forming a trace over the connector and the contact pad, the trace having a major axis extending in a direction substantially parallel to a major surface of the substrate, the trace spaced apart from the mounting pad in a direction substantially parallel to the major surface of the substrate, the connector electrically interposed between the trace and the mounting pad; forming a mounting structure on the mounting pad; and disposing a molding compound over the trace and around the mounting structure, wherein the trace is formed at a first level, and the connector is formed at a second level below the first level.
 8. The method of claim 7, wherein the forming of the trace comprises: forming an insulating layer over the contact pad and the connector; and patterning a first opening and a second opening in the insulating layer, the contact pad being exposed in the first opening, the connector being exposed in the second opening.
 9. The method of claim 8, wherein the forming of the trace comprises forming a metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the contact pad and the connector.
 10. The method of claim 8, wherein the forming of the mounting pad comprises depositing a metal layer, the metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the connector.
 11. The method of claim 7, wherein the mounting pad is formed at the first level.
 12. The method of claim 7, wherein the contact pad is formed at the second level.
 13. The method of claim 7, further comprising: reshaping the molding compound such that a topmost surface of the molding compound is below a topmost surface of the mounting structure.
 14. A method of forming an interconnect structure, the method comprising: forming a connector over a substrate; forming a contact pad over the substrate; forming an insulating layer over the contact pad and the connector; forming a mounting pad over the connector, the mounting pad electrically coupled to the connector; forming a trace over the connector and the contact pad, the trace having a major axis extending in a direction substantially parallel to a major surface of the substrate, the trace spaced apart from the mounting pad in a direction substantially parallel to the major surface of the substrate, the connector electrically interposed between the trace and the mounting pad; forming a mounting structure on the mounting pad; and disposing a molding compound over the trace and around the mounting structure, wherein the mounting pad and the trace extend through the insulating layer.
 15. The method of claim 14, wherein the forming of the trace comprises forming a metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the contact pad and the connector.
 16. The method of claim 14, wherein the forming of the mounting pad comprises depositing a metal layer, the metal layer extending over an upper surface of the insulating layer, the metal layer extending through the insulating layer to the connector.
 17. The method of claim 14, wherein the contact pad and the connector are formed at a first level.
 18. The method of claim 17, wherein the trace and the mounting pad are formed at a second level.
 19. The method of claim 18, wherein the second level is below the first level.
 20. The method of claim 18, further comprising: reshaping the molding compound such that a topmost surface of the molding compound is below a topmost surface of the mounting structure. 